even if the dist. needs to be recalibrated that has nothing to do with the vacuum source. You dont want to hook the dist. up to full vac because it would allways be at full advance, limiting your bottom end. I've built alot of engines, high performance, street, and marine high performance and have allways hooked the dist. up to the correct carb port. Engine vacuum is not adjustable under the carb, by hooking up to the port that recieves the vacuum that is created in the veturis the dist. will advance with the throttle.